The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC), operating
in martian orbit since September 1997, acquired an image of the
Mars Exploration Rover (MER-A), Spirit, on 19 January 2004. The
Spirit/Columbia Memorial Station is clearly seen as a bright
feature in the image (above left two images, one annotated),
as are the parachute and backshell from
which Spirit was detached during the landing on 4 January 2004.
Also evident is a dark scar on the rim of a crater to the northeast
of the lander; this dark marking was not present prior to landing,
and is believed to have been caused by the impact of Spirit's heatshield.
The lander is white because the data received from Mars were
saturated at this location--that is, the lander was so much
brighter than the surrounding
terrain that the camera saw it as a white object.

The MGS MOC image was combined with the third MER-A descent image
(DIMES #3; DIMES = Descent Image Motion Estimation System)
to make a stereo anaglyph (right, two
images, one annotated; 3-d red/blue glasses necessary for stereo effect)
of the landing site. The DIMES image was acquired at an altitude of
about 1.4 km (~0.9 mi) above the surface on 4 January as Spirit
was descending. The DIMES image shows the heatshield
(see annotated views, above) as it was falling away from the lander; this
shows up in the 3-d picture as a dark blue/black feature. The DIMES
image also showed the shadow of Spirit's open parachute as it
was descending (see annotated views above). The heatshield in the DIMES
image was in the air, approximately 600 m (~1970 ft) away from the lander.
Neither the parachute shadow nor the heatshield are seen in the MOC image
acquired 19 January. However, features related to the
lander that were not in the DIMES image but appear in the MOC view
include: the lander, the backshell and parachute, the impact scar
made by the heatshield after it hit the ground, and some of the
initial bounce marks made by Spirit's airbags.

The MOC image of the Spirit lander and its landing site was acquired
using a new technique that was pioneered by the MGS project in 2003. Called
"cPROTO" (for Pitch and Roll Only Targeted Observation with planetary motion compensation),
the approach allows MOC,
which normally takes pictures 1.5 meters (5 feet)
per pixel to 12 meters (40 feet) per pixel, to acquire images with a
higher resolution.
By pitching the MGS spacecraft at a rate faster than it orbits
around Mars, and moving it in a way that compensates for
the rotation of the planet, MOC is able to obtain images
with a down-track resolution of about 50 cm/pixel (~20 inches/pixel),
although the cross-track resolution remains ~1.5 m/pixel (5 ft/pixel).
These images have a better signal-to-noise ratio than typical
1.5 m/pixel MOC images, as well. This
technique allows the lander and other details not normally visible
in a full-resolution MOC image to be seen. After Spirit landed,
the MGS MOC team made two attempts to image the lander using
the cPROTO method. The technique is still so new that it's quite
challenging to hit a target on the first try. Thus, the
first attempt, on 10 January 2004,
missed the lander by about 150 meters (~490 ft). The second attempt,
on 19 January 2004, got the lander and other features. The two
January 2004 cPROTO images have been mosaiced together (bottom
picture, above) to provide a nice overview of the landing site.
The light-toned features on the far right of the mosaic are
the hills seen to the southeast of the lander in
Spirit's early January panorama.

Each image shown here is located in Gusev Crater
near 14.7°S, 184.6°W. North is up and sunlight illuminates
each image from the left. The MOC images were acquired near 2
p.m. local time on Mars. The lander appears white because the DNs (data
numbers) received from Mars for the lander were 255--the maximum
possible (i.e., the lander was saturated). The values were
saturated because of the high sun elevation angle and the fact that
the lander and parachute are covered with highly reflective,
light-toned materials (as seen in the
lander portrait
released on 21 January 2004). In the annotated pictures,
the "DIMES 'First Bounce' Estimate" is the preliminary location where
Spirit's airbags were believed to have first hit the surface (a
revised location was expected to be reported at the Spirit
press briefing on Friday, 23 January 2004).
The "Surface Feature Localization" is the location of
the lander that was estimated by the MER-A team using sight lines to
landmarks in the lander's panoramic images. The MOC image shows that
the estimation by sightlines was good to better than 10 meters (~33 ft).
Note that the heatshield and parachute shadow are not visible in the
annotated MOC image, but appear in the stereo view made by combining
the DIMES and MOC images; also note the dark feature on the crater rim
(heatshield impact location), the airbag bounce marks, and the bright
features (lander, parachute, backshell) were visible to MOC but not
present on the surface when the DIMES image was acquired. To see each
of the two images used in the 3-d anaglyph as separate pictures, click
here for the DIMES image (left eye) and
here for the MOC image (right eye).
To see materials presented by Dr. Michael C. Malin at the 23 January 2004
Spirit press briefing, click here.

Malin Space Science Systems and the California Institute of Technology
built the MOC using spare hardware from the Mars Observer mission.
MSSS operates the camera from its facilities in San Diego, California.
The Jet Propulsion Laboratory's Mars Surveyor Operations Project
operates the Mars Global Surveyor spacecraft with its industrial
partner, Lockheed Martin Astronautics, from facilities in Pasadena,
California and Denver, Colorado.